Method for transmitting information for lte-wlan aggregation system and a device therefor

ABSTRACT

The present invention relates to a wireless communication system. More specifically, the present invention relates to a method and a device for transmitting information for LTE-WLAN aggregation system, the method comprising: triggering, by a PDCP entity, a status report for indicating flow control information for a WLAN link; setting, by the PDCP entity, a value of a FMS field in the status report to a PDCP SN of a first missing PDCP SDU; setting, by the PDCP entity, a value of a HRW field in the status report to the value of the FMS field if no PDCP SDUs have been received on the WLAN link; and generating and transmitting, by the PDCP entity, the status report including the HRW field.

CROSS-REFERENCE TO RELATED APPLICATIONS

Pursuant to 35 U.S.C. §119(e), this application claims the benefit ofU.S. Provisional Patent Application No. 62/300,917, filed on Feb. 28,2016, the contents of which are all hereby incorporated by referenceherein in its entirety.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a wireless communication system and,more particularly, to a method for transmitting information for LTE-WLANaggregation system and a device therefor.

Discussion of the Related Art

As an example of a mobile communication system to which the presentinvention is applicable, a 3rd Generation Partnership Project Long TermEvolution (hereinafter, referred to as LTE) communication system isdescribed in brief.

FIG. 1 is a view schematically illustrating a network structure of anE-UMTS as an exemplary radio communication system. An Evolved UniversalMobile Telecommunications System (E-UMTS) is an advanced version of aconventional Universal Mobile Telecommunications System (UMTS) and basicstandardization thereof is currently underway in the 3GPP. E-UMTS may begenerally referred to as a Long Term Evolution (LTE) system. Details ofthe technical specifications of UMTS and E-UMTS are provided in Release7 and Release 8 of “3rd Generation Partnership Project; TechnicalSpecification Group Radio Access Network”, for example.

Referring to FIG. 1, the E-UMTS includes a User Equipment (UE), eNode Bs(eNBs), and an Access Gateway (AG) which is located at an end of thenetwork (E-UTRAN) and connected to an external network. The eNBs maysimultaneously transmit multiple data streams for a broadcast service, amulticast service, and/or a unicast service.

One or more cells may exist per eNB. The cell is set to operate in oneof bandwidths such as 1.25, 2.5, 5, 10, 15, and 20 MHz and provides adownlink (DL) or uplink (UL) transmission service to a plurality of UEsin the bandwidth. Different cells may be set to provide differentbandwidths. The eNB controls data transmission or reception to and froma plurality of UEs. The eNB transmits DL scheduling information of DLdata to a corresponding UE so as to inform the UE of a time/frequencydomain in which the DL data is supposed to be transmitted, coding, adata size, and hybrid automatic repeat and request (HARQ)-relatedinformation. In addition, the eNB transmits UL scheduling information ofUL data to a corresponding UE so as to inform the UE of a time/frequencydomain which may be used by the UE, coding, a data size, andHARQ-related information. An interface for transmitting user traffic orcontrol traffic may be used between eNBs. A core network (CN) mayinclude the AG and a network node or the like for user registration ofUEs. The AG manages the mobility of a UE on a tracking area (TA) basis.One TA includes a plurality of cells.

Meanwhile, various wireless communication technologies systems have beendeveloped with rapid development of information communicationtechnologies. WLAN technology from among wireless communicationtechnologies allows wireless Internet access at home or in enterprisesor at a specific service provision region using mobile terminals, suchas a Personal Digital Assistant (PDA), a laptop computer, a PortableMultimedia Player (PMP), etc. on the basis of Radio Frequency (RF)technology.

A standard for a wireless LAN technology is developing as IEEE(Institute of Electrical and Electronics Engineers) 802.11 standard.IEEE 802.11a and b use an unlicensed band on 2.4 GHz or 5 GHz. IEEE802.11b provides transmission speed of 11 Mbps and IEEE 802.11a providestransmission speed of 54 Mbps. IEEE 802.11g provides transmission speedof 54 Mbps in a manner of applying an OFDM (orthogonalfrequency-division multiplexing) scheme on 2.4 GHz. IEEE 802.11nprovides transmission speed of 300 Mbps to 4 spatial streams in a mannerof applying a MIMO-OFDM (multiple input multiple output-OFDM) scheme.IEEE 802.11n supports a channel bandwidth as wide as 40 MHz. In thiscase, it is able to provide transmission speed of 600 Mbps.

The aforementioned wireless LAN standard has been continuously enhancedand standardization of IEEE 802.11ax, which is appearing after IEEE802.11ac standard supporting maximum 1 Gbps by using maximum 160 MHzchannel bandwidth and supporting 8 spatial streams, is under discussion.

Recently, a radio technology has been developed in two types in responseto the rapid increase of traffic. Firstly, speed of the radio technologyitself is getting faster. A mobile phone wireless internet technologyhas been developed from HSPA to LTE and LTE to LTE-A. Currently, themobile phone wireless internet technology becomes fast as fast asmaximum 225 Mbps and a Wi-Fi technology becomes fast as fast as maximum6.7 Gbps in case of IEEE 802.11 ad. Secondly, speed can be increasedusing a scheme of aggregating a plurality of radio channels with eachother. For example, there exists LTE-A which supports carrieraggregation corresponding to a technology of binding frequency bandsusing an identical radio technology into one. In this context, necessityfor a technology of aggregating heterogeneous wireless internet isemerging. It is necessary to develop a scheme of transmitting data bybiding radio technologies (e.g., LTE and wireless-LAN) includingcharacteristics different from each other.

SUMMARY OF THE INVENTION

The object of the present invention can be achieved by providing amethod for User Equipment (UE) operating in a wireless communicationsystem as set forth in the appended claims.

In another aspect of the present invention, provided herein is acommunication apparatus as set forth in the appended claims.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention.

FIG. 1 is a diagram showing a network structure of an Evolved UniversalMobile Telecommunications System (E-UMTS) as an example of a wirelesscommunication system;

FIG. 2A is a block diagram illustrating network structure of an evolveduniversal mobile telecommunication system (E-UMTS), and FIG. 2B is ablock diagram depicting architecture of a typical E-UTRAN and a typicalEPC;

FIG. 3 is a diagram showing a control plane and a user plane of a radiointerface protocol between a UE and an E-UTRAN based on a 3rd generationpartnership project (3GPP) radio access network standard;

FIG. 4 is a diagram of an example physical channel structure used in anE-UMTS system;

FIGS. 5, 6 and 7 illustrate exemplary configurations of an IEEE 802.11system to which the present invention is applicable;

FIG. 8 illustrates an exemplary configuration of a WLAN system;

FIG. 9 is a block diagram of a communication apparatus according to anembodiment of the present invention;

FIG. 10 is a diagram for a LTE-WLAN aggregation (LWA) Radio ProtocolArchitecture according to embodiments of the present invention;

FIGS. 11A, 11B and 11C are diagrams for PDCP control PDU for PDCP statusreport;

FIGS. 12A, 12B and 12C are diagrams for PDCP control PDU for LWA statusreport; and

FIGS. 13 and 14 are diagrams for transmitting information for LTE-WLANaggregation system according to embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Universal mobile telecommunications system (UMTS) is a 3rd Generation(3G) asynchronous mobile communication system operating in wideband codedivision multiple access (WCDMA) based on European systems, globalsystem for mobile communications (GSM) and general packet radio services(GPRS). The long-term evolution (LTE) of UMTS is under discussion by the3rd generation partnership project (3GPP) that standardized UMTS.

The 3GPP LTE is a technology for enabling high-speed packetcommunications. Many schemes have been proposed for the LTE objectiveincluding those that aim to reduce user and provider costs, improveservice quality, and expand and improve coverage and system capacity.The 3G LTE requires reduced cost per bit, increased serviceavailability, flexible use of a frequency band, a simple structure, anopen interface, and adequate power consumption of a terminal as anupper-level requirement.

Hereinafter, structures, operations, and other features of the presentinvention will be readily understood from the embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings. Embodiments described later are examples in which technicalfeatures of the present invention are applied to a 3GPP system.

Although the embodiments of the present invention are described in thecontext of a long term evolution (LTE) system and a LTE-advanced (LTE-A)system in the present specification, they are purely exemplary.Therefore, the embodiments of the present invention are applicable toany other communication system corresponding to the above definition. Anexemplary system in which the invention disclosed herein may beimplemented is a system compliant with the 3GPP specification TS 36.321Version 12.6.0. In addition, although the embodiments of the presentinvention are described based on a frequency division duplex (FDD)scheme in the present specification, the embodiments of the presentinvention may be easily modified and applied to a half-duplex FDD(H-FDD) scheme or a time division duplex (TDD) scheme.

FIG. 2A is a block diagram illustrating network structure of an evolveduniversal mobile telecommunication system (E-UMTS). The E-UMTS may bealso referred to as an LTE system. The communication network is widelydeployed to provide a variety of communication services such as voice(VoIP) through IMS and packet data.

As illustrated in FIG. 2A, the E-UMTS network includes an evolved UMTSterrestrial radio access network (E-UTRAN), an Evolved Packet Core (EPC)and one or more user equipment. The E-UTRAN may include one or moreevolved NodeB (eNodeB) 20, and a plurality of user equipment (UE) 10 maybe located in one cell. One or more E-UTRAN mobility management entity(MME)/system architecture evolution (SAE) gateways 30 may be positionedat the end of the network and connected to an external network.

As used herein, “downlink” refers to communication from eNodeB 20 to UE10, and “uplink” refers to communication from the UE to an eNodeB. UE 10refers to communication equipment carried by a user and may be alsoreferred to as a mobile station (MS), a user terminal (UT), a subscriberstation (SS) or a wireless device.

FIG. 2B is a block diagram depicting architecture of a typical E-UTRANand a typical EPC.

As illustrated in FIG. 2B, an eNodeB 20 provides end points of a userplane and a control plane to the UE 10. MME/SAE gateway 30 provides anend point of a session and mobility management function for UE 10. TheeNodeB and MME/SAE gateway may be connected via an S1 interface.

The eNodeB 20 is generally a fixed station that communicates with a UE10, and may also be referred to as a base station (BS) or an accesspoint. One eNodeB 20 may be deployed per cell. An interface fortransmitting user traffic or control traffic may be used between eNodeBs20.

The MME provides various functions including NAS signaling to eNodeBs20, NAS signaling security, AS Security control, Inter CN node signalingfor mobility between 3GPP access networks, Idle mode UE Reachability(including control and execution of paging retransmission), TrackingArea list management (for UE in idle and active mode), PDN GW andServing GW selection, MME selection for handovers with MME change, SGSNselection for handovers to 2G or 3G 3GPP access networks, Roaming,Authentication, Bearer management functions including dedicated bearerestablishment, Support for PWS (which includes ETWS and CMAS) messagetransmission. The SAE gateway host provides assorted functions includingPer-user based packet filtering (by e.g. deep packet inspection), LawfulInterception, UE IP address allocation, Transport level packet markingin the downlink, UL and DL service level charging, gating and rateenforcement, DL rate enforcement based on APN-AMBR. For clarity MME/SAEgateway 30 will be referred to herein simply as a “gateway,” but it isunderstood that this entity includes both an MME and an SAE gateway.

A plurality of nodes may be connected between eNodeB 20 and gateway 30via the S1 interface. The eNodeBs 20 may be connected to each other viaan X2 interface and neighboring eNodeBs may have a meshed networkstructure that has the X2 interface.

As illustrated, eNodeB 20 may perform functions of selection for gateway30, routing toward the gateway during a Radio Resource Control (RRC)activation, scheduling and transmitting of paging messages, schedulingand transmitting of Broadcast Channel (BCCH) information, dynamicallocation of resources to UEs 10 in both uplink and downlink,configuration and provisioning of eNodeB measurements, radio bearercontrol, radio admission control (RAC), and connection mobility controlin LTE_ACTIVE state. In the EPC, and as noted above, gateway 30 mayperform functions of paging origination, LTE-IDLE state management,ciphering of the user plane, System Architecture Evolution (SAE) bearercontrol, and ciphering and integrity protection of Non-Access Stratum(NAS) signaling.

The EPC includes a mobility management entity (MME), a serving-gateway(S-GW), and a packet data network-gateway (PDN-GW). The MME hasinformation about connections and capabilities of UEs, mainly for use inmanaging the mobility of the UEs. The S-GW is a gateway having theE-UTRAN as an end point, and the PDN-GW is a gateway having a packetdata network (PDN) as an end point.

FIG. 3 is a diagram showing a control plane and a user plane of a radiointerface protocol between a UE and an E-UTRAN based on a 3GPP radioaccess network standard. The control plane refers to a path used fortransmitting control messages used for managing a call between the UEand the E-UTRAN. The user plane refers to a path used for transmittingdata generated in an application layer, e.g., voice data or Internetpacket data.

A physical (PHY) layer of a first layer provides an information transferservice to a higher layer using a physical channel. The PHY layer isconnected to a medium access control (MAC) layer located on the higherlayer via a transport channel. Data is transported between the MAC layerand the PHY layer via the transport channel. Data is transported betweena physical layer of a transmitting side and a physical layer of areceiving side via physical channels. The physical channels use time andfrequency as radio resources. In detail, the physical channel ismodulated using an orthogonal frequency division multiple access (OFDMA)scheme in downlink and is modulated using a single carrier frequencydivision multiple access (SC-FDMA) scheme in uplink.

The MAC layer of a second layer provides a service to a radio linkcontrol (RLC) layer of a higher layer via a logical channel. The RLClayer of the second layer supports reliable data transmission. Afunction of the RLC layer may be implemented by a functional block ofthe MAC layer. A packet data convergence protocol (PDCP) layer of thesecond layer performs a header compression function to reduceunnecessary control information for efficient transmission of anInternet protocol (IP) packet such as an IP version 4 (IPv4) packet oran IP version 6 (IPv6) packet in a radio interface having a relativelysmall bandwidth.

A radio resource control (RRC) layer located at the bottom of a thirdlayer is defined only in the control plane. The RRC layer controlslogical channels, transport channels, and physical channels in relationto configuration, re-configuration, and release of radio bearers (RBs).An RB refers to a service that the second layer provides for datatransmission between the UE and the E-UTRAN. To this end, the RRC layerof the UE and the RRC layer of the E-UTRAN exchange RRC messages witheach other.

One cell of the eNB is set to operate in one of bandwidths such as 1.25,2.5, 5, 10, 15, and 20 MHz and provides a downlink or uplinktransmission service to a plurality of UEs in the bandwidth. Differentcells may be set to provide different bandwidths.

Downlink transport channels for transmission of data from the E-UTRAN tothe UE include a broadcast channel (BCH) for transmission of systeminformation, a paging channel (PCH) for transmission of paging messages,and a downlink shared channel (SCH) for transmission of user traffic orcontrol messages. Traffic or control messages of a downlink multicast orbroadcast service may be transmitted through the downlink SCH and mayalso be transmitted through a separate downlink multicast channel (MCH).

Uplink transport channels for transmission of data from the UE to theE-UTRAN include a random access channel (RACH) for transmission ofinitial control messages and an uplink SCH for transmission of usertraffic or control messages. Logical channels that are defined above thetransport channels and mapped to the transport channels include abroadcast control channel (BCCH), a paging control channel (PCCH), acommon control channel (CCCH), a multicast control channel (MCCH), and amulticast traffic channel (MTCH).

FIG. 4 is a view showing an example of a physical channel structure usedin an E-UMTS system. A physical channel includes several subframes on atime axis and several subcarriers on a frequency axis. Here, onesubframe includes a plurality of symbols on the time axis. One subframeincludes a plurality of resource blocks and one resource block includesa plurality of symbols and a plurality of subcarriers. In addition, eachsubframe may use certain subcarriers of certain symbols (e.g., a firstsymbol) of a subframe for a physical downlink control channel (PDCCH),that is, an L1/L2 control channel. In FIG. 4, an L1/L2 controlinformation transmission area (PDCCH) and a data area (PDSCH) are shown.In one embodiment, a radio frame of 10 ms is used and one radio frameincludes 10 subframes. In addition, one subframe includes twoconsecutive slots. The length of one slot may be 0.5 ms. In addition,one subframe includes a plurality of OFDM symbols and a portion (e.g., afirst symbol) of the plurality of OFDM symbols may be used fortransmitting the L1/L2 control information. A transmission time interval(TTI) which is a unit time for transmitting data is 1 ms.

A base station and a UE mostly transmit/receive data via a PDSCH, whichis a physical channel, using a DL-SCH which is a transmission channel,except a certain control signal or certain service data. Informationindicating to which UE (one or a plurality of UEs) PDSCH data istransmitted and how the UE receive and decode PDSCH data is transmittedin a state of being included in the PDCCH.

For example, in one embodiment, a certain PDCCH is CRC-masked with aradio network temporary identity (RNTI) “A” and information about datais transmitted using a radio resource “B” (e.g., a frequency location)and transmission format information “C” (e.g., a transmission blocksize, modulation, coding information or the like) via a certainsubframe. Then, one or more UEs located in a cell monitor the PDCCHusing its RNTI information. And, a specific UE with RNTI “A” reads thePDCCH and then receive the PDSCH indicated by B and C in the PDCCHinformation.

FIG. 5 illustrates an exemplary configuration of an IEEE 802.11 systemto which the present invention is applicable.

The IEEE 802.11 architecture may include a plurality of components. AWLAN that supports Station (STA) mobility transparent to upper layersmay be provided through interaction between the components. A BasicService Set (BSS) is a basic building block of an IEEE 802.11 LAN. FIG.5 illustrates two BSSs, BSS1 and BSS2, each with two STAs that aremembers of the BSS (STA1 and STA2 are included in BSS1 and STA3 and STA4are included in BSS2). Each of the BSSs covers an area in which the STAsof the BSS maintain communication, as indicated by an oval. This areamay be referred to as a Basic Service Area (BSA). As an STA moves out ofits BSA, it can no longer communicate directly with other members of theBSA.

An Independent Basic Service Set (IBSS) is the most basic type of BSS inthe IEEE 802.11 LAN. For example, a minimum IBSS includes only two STAs.A BSS, BSS1 or BSS2 which is the most basic type without othercomponents in FIG. 1 may be taken as a major example of the IBSS. Thisconfiguration may be realized when STAs communicate directly. Becausethis type of LAN is often formed without pre-planning for only as longas the LAN is needed, it is often referred to as an ad hoc network.

The membership of an STA in a BSS may be dynamically changed when theSTA is powered on or off or the STA moves into or out of the coveragearea of the BSS. To be a member of the BSS, an STA may join the BSS bysynchronization. To access all services of a BSS infrastructure, the STAshould be associated with the BSS. This association may be dynamicallyperformed and may involve use of a Distributed System Service (DSS).

FIG. 6 illustrates another exemplary configuration of the IEEE 802.11system to which the present invention is applicable. In FIG. 6,components such as a Distribution System (DS), a Distribution SystemMedium (DSM), and an Access Point (AP) are added to the architectureillustrated in FIG. 5.

Physical (PHY) performance may limit direct STA-to-STA distances. Whilethis distance limitation is sufficient in some cases, communicationbetween STAs apart from each other by a long distance may be required.To support extended coverage, a DS may be deployed.

A DS is built from multiple BSSs that are interconnected. Specifically,a BSS may exist as a component of an extended network with a pluralityof BSSs, rather than it exists independently as illustrated in FIG. 5.

The DS is a logical concept and may be specified by the characteristicsof a DSM. In this regard, the IEEE 802.11 standard logicallydistinguishes a Wireless Medium (WM) from a DSM. Each logical medium isused for a different purpose by a different component. The IEEE 802.11standard does not define that these media should be the same ordifferent. The flexibility of the IEEE 802.11 LAN architecture (DSstructure or other network structures) may be explained in the sensethat a plurality of media are logically different. That is, the IEEE802.11 LAN architecture may be built in various manners and may bespecified independently of the physical characteristics of eachimplementation example.

The DS may support mobile devices by providing services needed to handleaddress to destination mapping and seamless integration of multipleBSSs.

An AP is an entity that enables its associated STAs to access a DSthrough a WM and that has STA functionality. Data may move between theBSS and the DS through the AP. For example, STA2 and STA3 illustrated inFIG. 2 have STA functionality and provide a function of enablingassociated STAs (STA1 and STA4) to access the DS. Since all APs arebasically STAs, they are addressable entities. An address used by an APfor communication on the WM is not necessarily identical to an addressused by the AP for communication on the DSM.

Data that one of STAs associated with the AP transmits to an STA addressof the AP may always be received at an uncontrolled port and processedby an IEEE 802.1X port access entity. If a controlled port isauthenticated, transmission data (or frames) may be transmitted to theDS.

FIG. 7 illustrates another exemplary configuration of the IEEE 802.11system to which the present invention is applicable. In addition to thearchitecture illustrated in FIG. 6, FIG. 7 conceptually illustrates anExtended Service Set (ESS) to provide extended coverage.

A DS and BSSs allow IEEE 802.11 to create a wireless network ofarbitrary size and complexity. IEEE 802.11 refers to this type ofnetwork as an ESS network. An ESS may be a set of BSSs connected to asingle DS. However, the ESS does not the DS. The ESS network appears asan IBSS network to a Logical Link Control (LLC) layer. STAs within anESS may communicate with each other and mobile STAs may move from oneBSS to another (within the same ESS) transparently to the LLC layer.

IEEE 802.11 assumes nothing about the relative physical locations of theBSSs in FIG. 7. All of the followings are possible. The BSSs maypartially overlap. This is commonly used to arrange contiguous coverage.The BSSs may be physically disjointed. Logically, there is no limit tothe distance between BSSs. The BSSs may be physically co-located. Thismay be done to provide redundancy. One (or more) IBSS or ESS networksmay be physically present in the same space as one (or more) ESSnetworks. This may arise when an ad hoc network is operating at alocation that also has an ESS network, when physically overlapping IEEE802.11 networks have been set up by different organizations, or when twoor more different access and security policies are needed at the samelocation.

FIG. 8 illustrates an exemplary configuration of a WLAN system. In FIG.8, an exemplary infrastructure BSS including a DS is illustrated.

In the example of FIG. 8, an ESS includes BSS1 and BSS2. In the WLANsystem, an STA is a device complying with Medium Access Control/Physical(MAC/PHY) regulations of IEEE 802.11. STAs are categorized into AP STAsand non-AP STAs. The non-AP STAs are devices handled directly by users,such as laptop computers and mobile phones. In FIG. 8, STA1, STA3, andSTA4 are non-AP STAs, whereas STA2 and STAS are AP STAs.

In the following description, a non-AP STA may be referred to as aterminal, a Wireless Transmit/Receive Unit (WTRU), a User Equipment(UE), a Mobile Station (MS), a Mobile Terminal (MT), or a MobileSubscriber Station (MSS). An AP corresponds to a Base Station (BS), aNode B, an evolved Node B (eNB), a Base Transceiver System (BTS), or afemto BS in other wireless communication fields. FIG. 9 is a blockdiagram of a communication apparatus according to an embodiment of thepresent invention.

The apparatus shown in FIG. 9 can be a user equipment (UE) and/or eNBadapted to perform the above mechanism, but it can be any apparatus forperforming the same operation.

As shown in FIG. 9, the apparatus may comprises a DSP/microprocessor(110) and RF module (transmiceiver; 135). The DSP/microprocessor (110)is electrically connected with the transciver (135) and controls it. Theapparatus may further include power management module (105), battery(155), display (115), keypad (120), SIM card (125), memory device (130),speaker (145) and input device (150), based on its implementation anddesigner's choice.

Specifically, FIG. 9 may represent a UE comprising a receiver (135)configured to receive a request message from a network, and atransmitter (135) configured to transmit the transmission or receptiontiming information to the network. These receiver and the transmittercan constitute the transceiver (135). The UE further comprises aprocessor (110) connected to the transceiver (135: receiver andtransmitter).

Also, FIG. 9 may represent a network apparatus comprising a transmitter(135) configured to transmit a request message to a UE and a receiver(135) configured to receive the transmission or reception timinginformation from the UE. These transmitter and receiver may constitutethe transceiver (135). The network further comprises a processor (110)connected to the transmitter and the receiver. This processor (110) maybe configured to calculate latency based on the transmission orreception timing information.

FIG. 10 is a diagram for a LTE-WLAN aggregation (LWA) Radio ProtocolArchitecture according to embodiments of the present invention.

E-UTRAN supports LTE-WLAN aggregation (LWA) operation whereby a UE inRRC_CONNECTED is configured by the eNB to utilize radio resources of LTEand WLAN. Two scenarios are supported depending on the backhaulconnection between LTE and WLAN: i) non-collocated LWA scenario for anon-ideal backhaul and, ii) collocated LWA scenario for anideal/internal backhaul.

In LWA, the radio protocol architecture that a particular bearer usesdepends on the LWA backhaul scenario and how the bearer is set up. SplitLWA bearer is depicted on FIG. 10.

For DRBs mapped on RLC AM and for LWA bearers, the PDCP entity shall usethe reordering function as specified in this section when: i) the PDCPentity is associated with two AM RLC entities; or ii) the PDCP entity isconfigured for a LWA bearer; or iii) the PDCP entity is associated withone AM RLC entity after it was, according to the most recentreconfiguration, associated with two AM RLC entities or configured for aLWA bearer without performing PDCP re-establishment. The PDCP entityshall not use the reordering function in other cases.

The Split LWA bearer is a bearer whose radio protocols are located inboth the eNB and the WLAN to use both eNB and WLAN radio resources inLTE-WLAN Aggregation.

The Split LWA bearer comprises a PDCP entity, a RLC entity and a MACentity for the eNB and a LWAAP (LTE-WLAN Aggregation AdaptationProtocol) entity and a WLAN entity for the WLAN.

In the downlink, LWA supports split bearer operation where the PDCPsublayer of the UE supports in-sequence delivery of upper layer PDUsbased on the reordering procedure introduced for DC. In the uplink, PDCPPDUs can only be sent via the LTE.

The UE supporting LWA may be configured by the eNB to send PDCP statusreport or LWA status report, in cases where feedback from WT is notavailable.

FIG. 11 is a diagram for PDCP control PDU for PDCP status report.

For a transmission operation, when upper layers request a PDCPre-establishment, for radio bearers that are mapped on RLC AM, the UEshall compile a status report as indicated below after processing thePDCP Data PDUs that are received from lower layers due to there-establishment of the lower layers, and submit it to lower layers asthe first PDCP PDU for the transmission if the radio bearer isconfigured by upper layers to send a PDCP status report in the uplink,by: setting the FMS field to the PDCP SN of the first missing PDCP SDU,if there is at least one out-of-sequence PDCP SDU stored, allocating aBitmap field of length in bits equal to the number of PDCP SNs from andnot including the first missing PDCP SDU up to and including the lastout-of-sequence PDCP SDUs, rounded up to the next multiple of 8, or upto and including a PDCP SDU for which the resulting PDCP Control PDUsize is equal to 8188 bytes, whichever comes first, setting as ‘0’ inthe corresponding position in the bitmap field for all PDCP SDUs thathave not been received as indicated by lower layers, and optionally PDCPSDUs for which decompression have failed, and indicating in the bitmapfield as ‘1’ for all other PDCP SDUs.

For a receive operation, when a PDCP status report is received in thedownlink, for radio bearers that are mapped on RLC AM: for each PDCPSDU, if any, with the bit in the bitmap set to ‘1’, or with theassociated COUNT value less than the COUNT value of the PDCP SDUidentified by the FMS field, the successful delivery of thecorresponding PDCP SDU is confirmed, and the UE shall process the PDCPSDU.

The PDCP Control PDU is used to convey: i) a PDCP status reportindicating which PDCP SDUs are missing and which are not following aPDCP re-establishment, and ii) header compression control information,e.g. interspersed ROHC feedback.

FIG. 11A shows a format of the PDCP Control PDU carrying one PDCP statusreport when a 12 bit SN length is used, FIG. 11B shows the format of thePDCP Control PDU carrying one PDCP status report when a 15 bit SN lengthis used, and FIG. 11C shows the format of the PDCP Control PDU carryingone PDCP status report when an 18 bit SN length is used. This format isapplicable for DRBs mapped on RLC AM.

A D/C field indicates that whether the PDCP PDU is for a control PDU ora Data PDU. If a value of the D/C field is set to ‘0’, the PDCP PDU isfor Control PDU. Otherwise, the PDCP PDU is for a Data PDU.

A PDU type field indicates whether the PDCP control PDU is for PDCPstatus report or for Interspersed ROHC feedback packet. If a value ofthe PDU type field is set to ‘000’, the PDCP control PDU is for PDCPstatus report. If a value of the PDU type field is set to ‘001’, thePDCP control PDU is for Interspersed ROHC feedback packet.

A FMS field indicates a PDCP SN of the first missing PDCP SDU. A size ofthe FMS field is 12-bits when a 12 bit SN length is used, a size of theFMS field is 15-bits when a 15 bit SN length is used, and a size of theFMS field is 18-bits when an 18 bit SN length is used.

A most significant bit (MSB) of the first octet of the type “Bitmap”indicates whether or not the PDCP SDU with the SN (FMS+1) modulo(Maximum_PDCP_SN+1) has been received and, optionally decompressedcorrectly. A least significant bit (LSB) of the first octet of the type“Bitmap” indicates whether or not the PDCP SDU with the SN (FMS+8)modulo (Maximum_PDCP_SN+1) has been received and, optionallydecompressed correctly. If a bit of the bitmap indicates ‘0’, PDCP SDUwith PDCP SN=(FMS+bit position) modulo (Maximum_PDCP_SN+1) is missing inthe receiver. The bit position of Nth bit in the Bitmap is N, i.e., thebit position of the first bit in the Bitmap is 1.

If a bit of the bitmap indicates ‘1’, PDCP SDU with PDCP SN=(FMS+bitposition) modulo (Maximum_PDCP_SN+1) does not need to be retransmitted.The bit position of Nth bit in the Bitmap is N, i.e., the bit positionof the first bit in the Bitmap is 1.

The UE fills the bitmap indicating which SDUs are missing (unsetbit-‘0’), i.e. whether an SDU has not been received or optionally hasbeen received but has not been decompressed correctly, and which SDUs donot need retransmission (set bit-‘1’), i.e. whether an SDU has beenreceived correctly and may or may not have been decompressed correctly.

As mentioned before, The LTE-WLAN Aggregation (LWA) is designed based onthe Dual Connectivity (DC), where the UE PDCP receives PDCP PDUs fromtwo path, one from LTE and the other from WLAN.

One important function for the PDCP is flow control. The PDCPtransmitter must control the number of PDCP PDUs being transmitted lessthan the half of the PDCP SN space so that the successfully transmittedPDCP PDUs are not discarded by the PDCP receiver. When the lastdelivered PDCP SDU to upper layer in the PDCP receiver is SN=X, if thePDCP receiver receives PDCP SDU with SN>=X+Window (=half of PDCP SNspace), the PDCP receiver discards the received PDCP SDU because it isoutside of the Window.

However, since the WLAN side is not under control of eNB, the flowcontrol between eNB and WLAN AP is difficult to realize. Thus, some ofthe prior arts suggest for the UE PDCP to send PDCP status reportperiodically to the eNB PDCP. The PDCP status report consists of FirstMissing PDCP SN (FMS) and BITMAP which represents reception status ofeach PDCP PDU following PDCP PDU with SN=FMS.

However, periodical transmission of PDCP status report is notradio-efficient. Most of the information is of no use for flow control,and periodical transmission of useless information on the radio is justwaste of radio resource.

FIG. 12 is a diagram for PDCP control PDU for LWA status report.

When PDCP Data PDU with polling bit P set to 1 is received, the UE shallcompile and transmit the PDCP status report if configured to send thePDCP status report in response to polling (statusPDU-TypeForPolling isconfigured and set to type1). Else if configured to send the LWA statusreport in response to polling (statusPDU-TypeForPolling is configuredand set to type2, the UE shall compile and transmit the LWA statusreport.

When t-StatusReportType1 expires, the UE shall compile and transmit thePDCP status report, and start t-StatusReportType1 with valuestatusPDU-Periodicity-Type1. When t-StatusReportType2 expires, the UEshall compile and transmit the LWA status report, and startt-StatusReportType2 with value statusPDU-Periodicity-Type2.

When t-StatusReportType1 is configured or reconfigured by upper layers,the UE shall stop t-StatusReportType1, if running, and startt-StatusReportType1 with value statusPDU-Periodicity-Type1. Whent-StatusReportType2 is configured or reconfigured by upper layers, theUE shall stop t-StatusReportType2, if running, and startt-StatusReportType2 with value statusPDU-Periodicity-Type2 plusstatusPDU-Periodicity-Offset if statusPDU-Periodicity-Offset isconfigured by upper layers, or else, the UE shall startt-StatusReportType2 with value statusPDU-Periodicity-Type2.

When periodic PDCP status report becomes disabled by upper layers, theUE shall stop t-StatusReportType1, if running, and stopt-StatusReportType2, if running.

When LWA status report is triggered, the UE shall compile a statusreport as indicated below, and submit it to lower layers as the firstPDCP PDU for the transmission, by i) setting the FMS field to the PDCPSN of the first missing PDCP SDU, ii) setting the HRW field to the PDCPSN of the PDCP SDU received on WLAN with highest PDCP COUNT value.

FIG. 12A shows the format of the PDCP Control PDU carrying one LWAstatus report when a 12 bit SN length is used, FIG. 12B shows the formatof the PDCP Control PDU carrying one LWA status report when a 15 bit SNlength is used, and FIG. 12C shows the format of the PDCP Control PDUcarrying one LWA status report when an 18 bit SN length is used. Thisformat is applicable for LWA DRBs.

A D/C field indicates that whether the PDCP PDU is for a control PDU ora Data PDU. If a value of the D/C field is set to ‘0’, the PDCP PDU isfor Control PDU. Otherwise, the PDCP PDU is for a Data PDU.

A PDU type field indicates whether the PDCP control PDU is for PDCPstatus report or for Interspersed ROHC feedback packet. If a value ofthe PDU type field is set to ‘000’, the PDCP control PDU is for PDCPstatus report. If a value of the PDU type field is set to ‘001’, thePDCP control PDU is for Interspersed ROHC feedback packet.

A FMS (First missing PDCP SN) field indicates a PDCP SN of the firstmissing PDCP SDU. A size of the FMS field is 12-bits when a 12 bit SNlength is used, a size of the FMS field is 15-bits when a 15 bit SNlength is used, and a size of the FMS field is 18-bits when an 18 bit SNlength is used.

A HRW (Highest Received PDCP SN on WLAN) field indicates a PDCP SN ofthe PDCP SDU received on WLAN with highest associated PDCP COUNT value.A size of the HRW field is 12 bits when a 12 bit SN length is used, 15bits when a 15 bit SN length is used and 18 bits when an 18 bit SNlength is used.

For DRBs mapped on RLC AM, when the reordering function is used, atreception of a PDCP Data PDU from lower layers: if received PDCPSN−Last_Submitted_PDCP_RX_SN>Reordering_Window or0<=Last_Submitted_PDCP_RX_SN−received PDCP SN<Reordering_Window, and ifthe PDCP PDU was received on WLAN, if received PDCP SN>Next_PDCP_RX_SN,for the purpose of setting the HRW field in the LWA status report, theUE shall use COUNT based on RX_HFN−1 and the received PDCP SN. Ifreceived PDCP SN<=Next_PDCP_RX_SN, for the purpose of setting the HRWfield in the LWA status report, the UE shall use COUNT based on RX_HFNand the received PDCP SN.

A NMP (Number of Missing PDCP SDUs) field is the number of missing PDCPSDU(s) with associated COUNT value below the associated COUNT valuecorresponding to HRW, starting from and including the associated COUNTvalue corresponding to FMS.

R field is a reserved field. The reserved bits shall be set to 0.Reserved bits shall be ignored by the receiver.

In LWA, a LWA status report is introduced in PDCP to perform flowcontrol in WLAN link. The LWA status report is composed of FMS, HRW, andNMP fields, and one issue is how to set the HRW field when no PDCP SDUshave been received on WLAN.

-   -   setting the HRW field to the PDCP SN of the PDCP SDU received on        WLAN with highest PDCP COUNT value or X, if no SDUs have been        received on WLAN;

Currently, two candidates are considered for X:

1. Maximum_PDCP_SN

2. (FMS+Reordering_Window) mod (Maximum_PDCP_SN+1)

However, those two candidates may not be used for indicating “no SDUshave been received on WLAN” in some cases, e.g. the Maximum_PDCP_SN iswithin the Reordering_Window, or the transmitter sends more PDCP SDUsthan half of the PDCP SN space. Thus, another value of HRW needs to beused to indicate that “no SDUs have been received on WLAN”.

FIGS. 13 and 14 are diagrams for transmitting information for LTE-WLANaggregation system according to embodiments of the present invention.

It is invented that when the UE (transmitter of LWA status report) wantsto indicate in the LWA status report that no PDCP SDUs have beenreceived on WLAN, the UE sets the HRW to FMS, i.e. the PDCP SN of thefirst missing PDCP SDU. In other words, the value of the HRW field isset equal to the value of the FMS field in the LWA status report.

When the eNB (receiver of LWA status report) receives the LWA statusreport including HRW field whose value is set equal to the value of FMSfield, the eNB considers that no PDCP SDUs have been received by the UEvia WLAN link. Otherwise (i.e. the value of HRW field is different fromthe value of FMS field), the eNB considers that PDCP SDUs up to the PDCPSDU with PDCP SN=HRW have been received by the UE.

There are two options according to embodiments of the present invention.

Option 1 of FIG. 13 is setting a value of a HRW field in the statusreport to the value of a FMS field after setting a value of a FMS fieldin the status report to a PDCP SN of a first missing PDCP SDU if no PDCPSDUs have been received on the WLAN link.

When a status report for indicating flow control information for a WLANlink is triggered (S1301), the UE sets a value of a FMS field in thestatus report to a PDCP SN of a first missing PDCP SDU (S1303). If noPDCP SDUs have been received on the WLAN link, the UE sets a value of aHRW field in the status report to the value of a FMS field (S1305).

If there are PDCP SDUs received on the WLAN link, the UE sets a value ofthe HRW field is set to a PDCP SN of a PDCP SDU received on the WLANwith a highest PDCP COUNT value (S1307).

And then the UE generates and transmits the status report including theHRW field (S1309).

Preferably, the UE is configured for using Long Term Evolution (LTE)link and WLAN link simultaneously for data reception, and the statusreport is a LWA status report.

Preferably, the status report further includes the FMS field.

Preferably, the PDCP SN of the first missing PDCP SDU is a PDCP SN of alast PDCP SDU delivered to an upper layer plus 1.

Option 2 of FIG. 14 is setting a value of a HRW field in the statusreport to a PDCP SN of a first missing PDCP SDU if no PDCP SDUs havebeen received on the WLAN link without considering setting of a value ofFMS.

When a status report for indicating flow control information for a WLANlink is triggered (S1401), the UE sets a first missing PDCP SDU if noPDCP SDUs have been received on the WLAN link (S1403).

If there are PDCP SDUs received on the WLAN link, the UE sets a value ofthe HRW field is set to a PDCP SN of a PDCP SDU received on the WLANwith a highest PDCP COUNT value (S1405).

In this case the UE can set a value of a FMS field in the status reportto a PDCP SN of a first missing PDCP SDU.

And then the UE generates and transmits the status report including theHRW field (S1407).

Preferably, the UE is configured for using Long Term Evolution (LTE)link and WLAN link simultaneously for data reception, and the statusreport is a LWA status report.

Preferably, the status report further includes the FMS field.

Preferably, the PDCP SN of the first missing PDCP SDU is a PDCP SN of alast PDCP SDU delivered to an upper layer plus 1.

When there is no PDCP SDUs received on the WLAN link, there was a lot ofdiscussion about what value to set the HRW field value.

What is needed is a special value of HRW that can indicate other thanhighest SN on WLAN. Considering that PDCP SN can wrap-around, we thinkthe only value that can have special meaning for HRW is “FMS”, i.e. setHRW equal to FMS when nothing have been received on WLAN link. All othervalues may or may not be considered invalid depending on the reorderingwindow and number of transmitted SDUs.

The embodiments of the present invention described hereinbelow arecombinations of elements and features of the present invention. Theelements or features may be considered selective unless otherwisementioned. Each element or feature may be practiced without beingcombined with other elements or features. Further, an embodiment of thepresent invention may be constructed by combining parts of the elementsand/or features. Operation orders described in embodiments of thepresent invention may be rearranged. Some constructions of any oneembodiment may be included in another embodiment and may be replacedwith corresponding constructions of another embodiment. It is obvious tothose skilled in the art that claims that are not explicitly cited ineach other in the appended claims may be presented in combination as anembodiment of the present invention or included as a new claim bysubsequent amendment after the application is filed.

In the embodiments of the present invention, a specific operationdescribed as performed by the BS may be performed by an upper node ofthe BS. Namely, it is apparent that, in a network comprised of aplurality of network nodes including a BS, various operations performedfor communication with an MS may be performed by the BS, or networknodes other than the BS. The term ‘eNB’ may be replaced with the term‘fixed station’, ‘Node B’, ‘Base Station (BS)’, ‘access point’, etc.

The above-described embodiments may be implemented by various means, forexample, by hardware, firmware, software, or a combination thereof.

In a hardware configuration, the method according to the embodiments ofthe present invention may be implemented by one or more ApplicationSpecific Integrated Circuits (ASICs), Digital Signal Processors (DSPs),Digital Signal Processing Devices (DSPDs), Programmable Logic Devices(PLDs), Field Programmable Gate Arrays (FPGAs), processors, controllers,microcontrollers, or microprocessors.

In a firmware or software configuration, the method according to theembodiments of the present invention may be implemented in the form ofmodules, procedures, functions, etc. performing the above-describedfunctions or operations. Software code may be stored in a memory unitand executed by a processor. The memory unit may be located at theinterior or exterior of the processor and may transmit and receive datato and from the processor via various known means.

Those skilled in the art will appreciate that the present invention maybe carried out in other specific ways than those set forth hereinwithout departing from the scope of the present invention. The aboveembodiments are therefore to be construed in all aspects as illustrativeand not restrictive. The scope of the invention should be determined bythe appended claims, not by the above description, and all changescoming within the meaning of the appended claims are intended to beembraced therein.

What is claimed is:
 1. A method for a user equipment (UE) operating in awireless communication system, the method comprising: triggering, by aPacket Data Convergence Protocol (PDCP) entity, a status report forindicating flow control information for a Wireless-LAN (WLAN) link;setting, by the PDCP entity, a value of a First Missing PDCP SequenceNumber (FMS) field in the status report to a PDCP Sequence Number (SN)of a first missing PDCP Service Data Unit (SDU); setting, by the PDCPentity, a value of a Highest Received PDCP SN on WLAN (HRW) field in thestatus report to the value of the FMS field if no PDCP SDUs have beenreceived on the WLAN link; and generating and transmitting, by the PDCPentity, the status report including the HRW field.
 2. The methodaccording to claim 1, wherein the UE is configured for using Long TermEvolution (LTE) link and WLAN link simultaneously for data reception. 3.The method according to claim 1, wherein a value of the HRW field is setto a PDCP SN of a PDCP SDU received on the WLAN with a highest PDCPCOUNT value if there are PDCP SDUs received on the WLAN link.
 4. Themethod according to claim 1, wherein the status report further includesthe FMS field.
 5. The method according to claim 1, wherein the PDCP SNof the first missing PDCP SDU is a PDCP SN of a last PDCP SDU deliveredto an upper layer plus
 1. 6. The method according to claim 1, whereinthe status report is a LTE-WLAN Aggregation (LWA) status report.
 7. Amethod for a user equipment (UE) operating in a wireless communicationsystem, the method comprising: triggering, by a Packet Data ConvergenceProtocol (PDCP) entity, a status report for indicating flow controlinformation for a Wireless-LAN (WLAN) link; setting, by the PDCP entity,a value of a Highest Received PDCP SN on WLAN (HRW) field in the statusreport to a PDCP Sequence Number (SN) of a first missing PDCP ServiceData Unit (SDU) if no PDCP SDUs have been received on the WLAN link; andgenerating and transmitting, by the PDCP entity, the status reportincluding the HRW field.
 8. The method according to claim 7, wherein theUE is configured for using Long Term Evolution (LTE) link and WLAN linksimultaneously for data reception.
 9. The method according to claim 7,wherein a value of the HRW field is set to a PDCP SN of a PDCP SDUreceived on the WLAN with a highest PDCP COUNT value if there are PDCPSDUs received on the WLAN link.
 10. The method according to claim 7,wherein the status report is a LTE-WLAN Aggregation (LWA) status report.11. A User Equipment (UE) for operating in a wireless communicationsystem, the UE comprising: a Radio Frequency (RF) module; and aprocessor operably coupled with the RF module and configured to: triggera status report for indicating flow control information for aWireless-LAN (WLAN) link, set a value of a First Missing PDCP SequenceNumber (FMS) field in the status report to a Packet Data ConvergenceProtocol (PDCP) Sequence Number (SN) of a first missing PDCP ServiceData Unit (SDU), set a value of a Highest Received PDCP SN on WLAN (HRW)field in the status report to the value of the FMS field if no PDCP SDUshave been received on the WLAN link, and generate and transmit thestatus report including the HRW field.
 12. A User Equipment (UE) foroperating in a wireless communication system, the UE comprising: a RadioFrequency (RF) module; and a processor operably coupled with the RFmodule and configured to: trigger a status report for indicating flowcontrol information for a Wireless-LAN (WLAN) link, set a value of aHighest Received PDCP SN on WLAN (HRW) field in the status report to aPacket Data Convergence Protocol (PDCP) Sequence Number (SN) of a firstmissing PDCP Service Data Unit (SDU) if no PDCP SDUs have been receivedon the WLAN link, generate and transmit the status report including theHRW field.